Multilayer substrate including components therein

ABSTRACT

Components having different heights are installed in a multilayer substrate using a metal core layer formed by bonding a plurality of metal layers. The metal core layer includes through-holes and a spot-faced portion. Passive components and an active component are disposed in the through-holes and the spot-faced portion, respectively. These components are connected to conductive patterns formed on wiring layers, with connecting vias therebetween. Contact faces of each component with the connecting vias are controlled so as to be disposed at the same level with the metal layers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/114,781,filed Apr. 25, 2005, now U.S. Pat. No. ______. This application ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer substrate includingcomponents therein, and in particular, to a multilayer substrateincluding components therein that is useful for installing componentshaving different dimensions in the substrate.

2. Description of the Related Art

In order to achieve a high density mounting of electronic components, amultilayer substrate including components therein has been produced. Insuch a multilayer substrate including components therein, the componentsare embedded inside of the wiring substrate. For example, PCTPublication No. WO 03/103355 discloses a structure of such a multilayersubstrate including components therein. As shown in FIG. 5 in thispatent document, a component is installed in a through-hole formed in acore member composed of a metal. According to this structure, amultilayer substrate that is excellent in the protection of thecomponent and in the heat dissipation effect can be provided.

In addition, in order to adjust the height of the components to beinstalled, the above patent document discloses a structure including aheight-adjusting member 30 shown in FIG. 3. According to this structurein which the height of the component to be installed is adjusted, evenwhen components having different dimensions are installed, contactpositions of these components can be adjusted. Therefore, this structurecan be preferably used when contact holes for connecting in a face-upmanner are formed using a laser.

However, in the method using such a height-adjusting member, in additionto the step of disposing desired components to be installed, a step ofdisposing the height-adjusting member is required. Accordingly, animprovement is desired.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a multilayer substrateincluding components therein that is useful for installing componentshaving different dimensions in the substrate.

In order to achieve the above object, according to a first aspect of thepresent invention, in a multilayer substrate including componentstherein, the components are disposed in accommodating portion providedin a metal core, and both top and fear bottom faces of the metal coreand the accommodating portion are sealed with an insulating layer. Inthe multilayer substrate according to the first aspect of the presentinvention, the metal core includes a plurality of metal layers.

Herein, the accommodating portion include a through-hole penetrating thetop and bottom faces of the metal core and a spot-faced portion that isopened in either the top face or the bottom face of the metal core. Theaccommodating portion are formed so as to have shapes according to thedimension of the components to be installed therein. The accommodatingportion can be formed by etching the metal core.

The components disposed in the accommodating portion include activecomponents such as a transistor and an integrated circuit; and passivecomponents such as a capacitor, an inductor, and a filter. Thesecomponents can be appropriately selected. These components are disposedin the accommodating portion provided in the metal core and are sealedwith the insulating layer from both top and bottom faces of the metalcore.

The metal core protects the components, which are installed in theaccommodating portion when sealing with the insulating layer.Furthermore, the metal core has a preferable function to dissipatingheat of a component that generates heat and can also function as ashield of an active component. In addition, the metal core can be usedas a conductive pattern, a power supply line, or a ground (GND) line.The metal core is preferably composed of copper considering theworkability by etching, the mechanical rigidity, the heat dissipationeffect, and the conductivity.

According to the present invention, since the metal core is composed ofa plurality of metal layers, the etching of the metal core can beperformed stepwise. Therefore, the accommodating portion can be formedaccording to the height of the components. Unlike the known structureincluding the height-adjusting member disclosed in the above-citedpatent document, the height of the accommodating portion can be adjustedby etching the metal layers according to the structure of the presentinvention. Consequently, the production process can be simplified.Furthermore, the metal core can be etched stepwise in the presentinvention. Therefore, even when the etching aspect ratio is low, themetal core can be etched with a higher aspect ratio compared with ametal core composed of a single metal layer.

The plurality of metal layers is preferably bonded each other by a resinlayer therebetween. According to this structure, the resin layer canfunction as a protector while the metal layers are etched. Therefore,the plurality of metal layers being bonded together can be etchedstepwise. The resin layer is preferably composed of a material that hasetching resistance to the etchant used for etching the metal layers.More preferably, the resin layer is composed of a material having a highadhesiveness for the metal layers.

The plurality of metal layers forming the metal core preferably has thesame thickness. Such a structure can decrease the warping of the metalcore. When three metal layers are bonded together, a metal layerdisposed at the center of the metal core may have a thickness largerthan that of other two metal layers, which have the same thickness.

According to a second aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer, and the components are connected to a conductivepattern provided on the insulating layer with connecting vias providedin the insulating layer. In the multilayer substrate according to thesecond aspect of the present invention, the metal core includes a firstmetal layer and a second metal layer, the accommodating portion includea first accommodating portion formed by removing the first metal layerand a second accommodating portion formed by removing the first metallayer and the second metal layer, and the components include a firstcomponent disposed in the first accommodating portion and a secondcomponent disposed in the second accommodating portion.

The conductive pattern provided on the insulating layer may be providedon both top and bottom faces of the metal core. Alternatively, theconductive pattern may be provided on either the top face or the bottomface of the metal core. The installed components are preferablyconnected to the conductive pattern in a face-up manner. The connectingstructure with the face-up manner is also described in the above-citedpatent document. This specification includes the content described inthe patent document as a reference description of the present invention.

The first accommodating portion has a structure suitable for receiving acomponent having a small height. The first accommodating portion canreceive a component having a height corresponding to the thickness of asingle metal layer. When the metal core is formed by bonding a pluralityof metal layers with at least one resin layer therebetween, the resinlayer may also be removed to form the first accommodating portion.

The second accommodating portion has a structure suitable for receivinga component having a large height. The second accommodating portion canreceive a component having a height corresponding to the thickness of aplurality of metal layers. When the metal core is composed of at leastthree metal layers, the first and the second accommodating portion maybe formed as follows. For example, the first accommodating portion maybe formed by removing two metal layers and the second accommodatingportion may be formed by removing three metal layers. Thus, the numberof sheets to be removed in the second accommodating portion is largerthan that in the first accommodating portion. The present invention alsoincludes such an embodiment.

Contact faces of the first component and the second component with theconnecting vias are preferably disposed at the same level. Thisstructure allows the connecting vias to have a certain length. As aresult, contacts for the connecting vias can be formed in the insulatinglayer with a constant laser output.

According to a third aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer, and the components are connected to a conductivepattern provided on the insulating layer with connecting vias providedin the insulating layer. In the multilayer substrate according to thethird aspect of the present invention, the metal core includes a firstmetal layer and a second metal layer, the accommodating portion includea first accommodating portion formed by removing the first metal layerand a second accommodating portion formed by removing the first metallayer and the second metal layer, the components include a firstcomponent disposed in the first accommodating portion and a secondcomponent disposed in the second accommodating portion, and theconnecting vias include a via for heat dissipation connected to thesecond metal layer.

When the second metal layer is used as a foundation, the second metallayer can be utilized as a conductor for dissipating heat. Thus, when acomponent that significantly generates heat is disposed in the firstaccommodating portion, the generated heat can be preferably dissipated.Accordingly, the first component is preferably an active component andthe second component is preferably a passive component. In order to fixthe first component with the second metal layer, the first component ispreferably bonded with an adhesive having a high thermal conductivity orbonded with a thin adhesive layer.

According to a fourth aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer, and the components are connected to a conductivepattern provided on the insulating layer with connecting vias providedin the insulating layer. In the multilayer substrate according to thefourth aspect of the present invention, the metal core includes a firstmetal layer and a second metal layer bonded with a resin layertherebetween, the accommodating portion include a first accommodatingportion formed by removing the first metal layer and the resin layer anda second accommodating portion formed by removing the first metal layer,the second metal layer, and the resin layer, and the components includea first component disposed in the first accommodating portion and asecond component disposed in the second accommodating portion.

Thus, the accommodating portion are formed by removing the bonding resinlayer. This structure can bring the component disposed in the firstaccommodating portion closer to the second metal layer. Accordingly, thestability of mounting and the heat dissipation effect of the componentcan be improved.

According to a fifth aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer, and the components are connected to a conductivepattern provided on the insulating layer with connecting vias providedin the insulating layer. In the multilayer substrate according to thefifth aspect of the present invention, the metal core includes a firstmetal layer and a second metal layer bonded with a resin layertherebetween, the accommodating portion include a first accommodatingportion formed by removing the first metal layer and a secondaccommodating portion formed by removing the first metal layer, thesecond metal layer, and the resin layer, and the components include afirst component disposed in the first accommodating portion and a secondcomponent disposed in the second accommodating portion.

Thus, the accommodating portion including the bonding resin layer isformed. In such a case, the component can be fixed using the resinlayer. Consequently, the component can be arranged more accurately, andin addition, the arrangement process of the component can be simplified.

According to a sixth aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, and both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer. In the multilayer substrate according to the sixthaspect of the present invention, the metal core includes a first metallayer and a second metal layer bonded with a resin layer therebetween,and a through-hole conductor piercing the metal core is provided at anarea formed by removing the resin layer, the first metal layer, and thesecond metal layer.

Thus, the through-hole conductor piercing the metal core is provided. Asa result, the conductive patterns provided on both top and bottom facesof the metal core can be electrically connected to each other, therebyimproving the design flexibility of wiring. In addition, the first metallayer and the second metal layer may be connected to each other usingthis through-hole conductor so as to provide a GND layer including thesemetal layers.

The through-hole conductor may be provided with the insulating layer forsealing therebetween. In such a case, the through-hole conductor can beformed as follows. A through-hole formed in the metal core is sealedwith the insulating layer. A through-hole is formed by piercing thisinsulating layer by a laser or drilling. A conductor layer is thenformed on the side wall of the through-hole to form the through-holeconductor. Alternatively, the through-hole conductor may be formed byproviding a conductor layer on the side wall of the metal core exposedby etching.

According to a seventh aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, and both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer. In the multilayer substrate according to the seventhaspect of the present invention, the metal core includes a first metallayer and a second metal layer bonded with a resin layer therebetween,and a plurality of through-hole conductors piercing the metal core isprovided in a single area formed by removing the resin layer, the firstmetal layer, and the second metal layer, with the insulating layertherebetween.

Thus, a plurality of through-hole conductors is formed in a single areaprovided in the metal core. In such a case, the through-hole conductorscan be disposed at a high density, compared with the case where eachthrough-hole conductor is provided in a separate area. In the pluralityof through-hole conductors disposed in the single area, the centerdistance between the adjacent through-hole conductors is preferably lessthan three times of the thickness of one of the metal layers. In view ofthe etching aspect ratio of the metal layers, when the through-holeconductors are disposed with a small interval, it is desirable that aplurality of through-hole conductors is disposed in a single area. Asdescribed above, the restriction of the etching aspect ratio can berelieved using a metal core formed by bonding a plurality of metallayers. In addition, this structure is useful for disposing thethrough-hole conductors at a higher density.

According to an eighth aspect of the present invention, in a multilayersubstrate including a component therein, the component is disposed in aaccommodating portion provided in a metal core, and both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer. In the multilayer substrate according to the eighthaspect of the present invention, the metal core includes a first metallayer and a second metal layer bonded with a resin layer therebetween,the accommodating portion is formed by removing the resin layer, thefirst metal layer, and the second metal layer, and a through-holeconductor piercing the metal core is provided in the accommodatingportion including the component, with the insulating layer therebetween.

As described, by providing the through-hole conductor in the area wherethe component is disposed, a higher density mounting can be performed.The number of through-hole conductors provided in the accommodatingportion with the component may be two or more.

According to a ninth aspect of the present invention, in a multilayersubstrate including components therein, the components are disposed inaccommodating portion provided in a metal core, and both top and bottomfaces of the metal core and the accommodating portion are sealed with aninsulating layer. In the multilayer substrate according to the ninthaspect of the present invention, the metal core includes a first metallayer and a second metal layer bonded with a resin layer therebetweenand at least a part of each metal layer is shared as a GND layer.

Thus, the first metal layer and the second metal layer that areseparated by the bonded structure are shared as the GND layer. In such acase, a GND structure having a higher stability can be provided. Inorder to share this GND layer, the first metal layer and the secondmetal layer are preferably connected to each other with a through-holeconductor piercing the top and the bottom faces of the metal core.

The through-hole conductor may be formed in a through-hole provided inthe metal core, with an insulating layer therebetween. Alternatively,the through-hole conductor may be formed by performing a process, suchas plating, for providing a conductive layer in the side wall of athrough-hole provided in the metal core. Furthermore, instead of such athrough-hole conductor, electrical conductivity may be provided to theresin layer bonding the metal layers in order to connect to the metallayers each other. It is sufficient that these connecting processes areperformed in at least the area that is shared as the GND layer.

As described above, according to the present invention, even whencomponents having different heights are installed in a multilayersubstrate, the height of accommodating portion of the components can beadjusted with a simple method. Accordingly, the present invention canprovide a multilayer substrate that is suitable for installing variouscomponents therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of a multilayersubstrate according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a multilayersubstrate according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the structure of a multilayersubstrate according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the structure of a multilayersubstrate according to a fourth embodiment of the present invention.

FIG. 5 is a plan view showing the arrangement of through-hole conductors54-1 and 54-2 shown in FIG. 4.

FIG. 6 is a plan view showing the arrangement of through-hole conductors54-5 and 54-6 shown in FIG. 4.

FIG. 7 is a plan view showing a modification of the arrangement of thethrough-hole conductors 54-5 and 54-6 shown in FIG. 6.

FIGS. 8A to 8C are cross-sectional views showing first steps ofproducing a multilayer substrate according to the present invention.

FIGS. 9A and 9B are cross-sectional views showing second steps ofproducing the multilayer substrate according to the present invention.

FIGS. 10A and 10B are cross-sectional views showing third steps ofproducing the multilayer substrate according to the present invention.

FIGS. 11A and 11B are cross-sectional views showing fourth steps ofproducing the multilayer substrate according to the present invention.

FIGS. 12A and 12B are cross-sectional views showing examples using ametal core layer as a GND.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Multilayer substrates according to the present invention will now bedescribed in detail with reference to the attached drawings. The presentinvention is not limited to the following embodiments and can beappropriately modified.

FIG. 1 is a cross-sectional view showing the structure of a multilayersubstrate according to a first embodiment of the present invention. Asshown in FIG. 1, a multilayer substrate 10 according to the presentembodiment includes a metal core layer having metal layers 30-1 and 30-2and a bonding resin layer 32. The metal layers 30-1 and 30-2 composed ofa copper plate are bonded with the bonding resin layer 32 disposedtherebetween. Wiring layers 34-1 and 34-2 are disposed on the top faceand the bottom face of the metal core layer, respectively. The wiringlayers 34-1 and 34-2 include conductive patterns 50 provided on aninsulating member 36.

The metal core layer includes through-holes 40-1, 40-2, 40-3, and 40-4and a spot-faced portion 42. The inside of the through-hole 40-1 isfilled with the insulating member 36. Passive components 20-1 and 20-2are disposed in the through-holes 40-2 and 40-3, respectively. Athrough-hole conductor 54 piercing the top face and the bottom face ofthe metal core is disposed in the through-hole 40-4 so that the wiringlayer 34-1 is electrically connected to the wiring layer 34-2. An activecomponent 22 is disposed in the spot-faced portion 42. The inside of thethrough-hole conductor 54 may be filled with an insulating member (notshown).

The through-hole 40-1 serves as a cutting area when cut with a dicer. Inother words, the through-hole 40-1 is used when each circuit module isseparated from a wiring substrate produced as a multiple substrateincluding a plurality of the circuit modules. Another through-hole (notshown) for cutting with a dicer is provided at the right of thethrough-hole 40-4 in the same way.

In the above structure, the passive components 20-1 and 20-2 disposed inthe metal core are fixed on the insulating member 36 forming the wiringlayer 34-2, with an insulative adhesive 24-1 therebetween. The activecomponent 22 is fixed on the metal layer 30-2 with an adhesive 24-2 suchas silver (Ag) paste therebetween, the adhesive 24-2 having a heatdissipation effect and electrical conductivity. The insulating member 36is filled with spaces formed between these components and the metal corelayer. In addition, when a ground electrode is provided on the bottomface of the active component 22, the active component 22 can beconnected to the metal core serving as a ground layer, with the adhesive24-2 therebetween.

The passive components 20-1 and 20-2 and the active component 22disposed inside of the metal core layer are connected to the conductivepatterns 50 with connecting vias 52 provided inside of the insulatingmember 36. As shown in FIG. 1, each of the components is disposed sothat the contact faces with the connecting vias 52 are disposed at thesame level. This arrangement can be provided by the following structure.

The passive components 20-1 and 20-2 having a large height are disposedin the through-holes 40-2 and 40-3, respectively, formed by removing themetal layers 30-1 and 30-2 and the bonding resin layer 32. The activecomponent 22 having a small height is disposed in the spot-faced portion42 formed by removing the metal layer 30-1 and the bonding resin layer32. Accordingly, the difference in the heights between the passivecomponents and the active component is compensated by the presence orthe absence of the metal layer 30-2. As a result, the contact faces ofeach of the components with the connecting vias 52 are disposed at thesame level.

The metal layer 30-2 is connected to the conductive pattern 50 providedon the wiring layer 34-2, with the connecting vias 52 therebetween. Thismetal layer 30-2 serves as a ground (GND) layer or a heat-dissipatinglayer.

Thus, the metal core layer is formed by laminating a plurality of metallayers 30-1 and 30-2. As a result, even when each component has adifferent height, the contact faces with the connecting vias can becontrolled so as to be disposed at the same level. Furthermore, themetal layer 30-2 adjacent to the component having a small height can beused as a heat-dissipating conductor. Accordingly, this structure isparticularly effective in the case where an active component having aheight smaller than that of a passive component is used.

FIG. 2 is a cross-sectional view showing the structure of a multilayersubstrate according to a second embodiment of the present invention. Theembodiment shown in FIG. 2 is an example including a metal core layercomposed of three metal layers. Other structures are the same as thosein the above first embodiment. Therefore, the characteristic parts inthe present embodiment are mainly described in the following descriptionand the description and reference numerals in the figure in the sameparts as those in the first embodiment are omitted.

In the second embodiment, three metal layers 30-1, 30-2, and 30-3 arebonded with bonding resin layers 32-1 and 32-2 therebetween to form themetal core layer, The metal core layer includes spot-faced portions42-1, 42-2, and 42-3. The spot-faced portion 42-1 is formed by removingthe metal layers 30-1 and 30-2 and the bonding resin layers 32-1 and32-2. The spot-faced portion 42-2 is formed by removing the metal layers30-1 and 30-2 and the bonding resin layer 32-1. The spot-faced portion42-3 is formed by removing the metal layer 30-1 and the bonding resinlayer 32-1.

Three components 20-1, 20-2, and 22 are disposed in the spot-facedportions 42-1, 42-2, and 42-3, respectively. The contact faces of eachcomponent with the connecting vias are controlled so as to be disposedat the same level.

As described above, the use of three metal layers can increase thevariation of the height of the component. The present embodiment canalso be applied to the structure in which a component is installed in athrough-hole formed by removing all the metal layers.

FIG. 3 is a cross-sectional view showing the structure of a multilayersubstrate according to a third embodiment of the present invention.According to an example of the embodiment shown in FIG. 3, a componentand a through-hole conductor are disposed in the same through-hole, anda greater importance is given to the connection from the metal corelayer to the conductive pattern provided on the bottom face. Otherstructures are the same as those in the above first embodiment.Therefore, the characteristic parts in the present embodiment are mainlydescribed in the following description and the description and referencenumerals in the figure in the same parts as those in the firstembodiment are omitted.

In the third embodiment, a through-hole conductor 54-1 and a passivecomponent 20 are disposed in a through-hole 40-2 formed in the metalcore layer. The passive component 20 is connected to the conductivepattern on the top face, with a connecting via 52-1 therebetween. Thepassive component 20 is also connected to the conductive pattern on thebottom face, with a connecting via 52-2 therebetween.

In the same way, another connecting via 52-1 is provided at a placewhere the metal core layer is connected to the conductive pattern on thetop face. Also, another connecting via 52-2 is provided at a place wherethe metal core layer is connected to the conductive pattern on thebottom face. In addition, an active component 22 disposed in thespot-faced portion 42 and a through-hole conductor 54-2 disposed in thethrough-hole 40-3 are appropriately provided.

As described above, the component and the through-hole conductor aredisposed in the same through-hole. This structure can achieve a higherdensity mounting. Furthermore, the design flexibility of wiring can beimproved by utilizing the pattern on the bottom face effectively.

FIG. 4 is a cross-sectional view showing the structure of a multilayersubstrate according to a fourth embodiment of the present invention. Theembodiment shown in FIG. 4 is an example showing a variation of thearrangement of through-hole conductors piercing the metal core layer.Other structures are the same as those in the above first embodiment.Therefore, the characteristic parts in the present embodiment are mainlydescribed in the following description and the description and referencenumerals in the figure in the same parts as those in the firstembodiment are omitted.

The multilayer substrate according to the fourth embodiment has thefollowing structure. A through-hole conductor 54-1 is disposed in athrough-hole 40-1. A through-hole conductor 54-2 is disposed in athrough-hole 40-2. A passive component 20 and through-hole conductors54-3 and 54-4 are disposed in a through-hole 40-3. Through-holeconductors 54-5 and 54-6 are disposed in a through-hole 40-4.

Herein, the through-hole conductors 54-1 and 54-2 are disposed such thatthe center distance between the through-hole conductors is at least 3t,i.e., three times of t, wherein t represents the thickness of one of themetal layer. When the center distance between the through-holeconductors is at least 3t, the metal layers can be etched while themetal core layer remains between the through-hole conductors.Accordingly, each through-hole conductor is disposed in a separatethrough-hole. This structure is effective in the prevention ofinterference of signal lines.

In addition, the through-hole conductors 54-3 and 54-4, and thethrough-hole conductors 54-5 and 54-6 are disposed such that the centerdistance between the through-hole conductors is less than 3t,respectively. When the center distance between the through-holeconductors is less than 3t, it is difficult to etch the metal layerswhile the metal core layer remains between the through-hole conductors.Accordingly, a plurality of through-hole conductors is disposed in thesame through-hole at an interval of less than 3t to improve the mountingdensity. In such a case, as shown in FIG. 4, the through-hole conductors54-3 and 54-4 are disposed in the same through-hole 40-3 as in thecomponent 20, thereby further improving the mounting density.

FIG. 5 is a plan view showing the arrangement of through-hole conductors54-1 and 54-2 shown in FIG. 4. As shown in FIG. 5, these through-holeconductors 54-1 and 54-2 are concentrically disposed in the centers ofthe through-holes 40-1 and 40-2 piercing the metal layers 30,respectively. The distance between each center of the through-holeconductors 54-1 and 54-2 and each wall surface of the through-holes 40-1and 40-2 is at least the thickness t of one of the metal layer. Aninsulating member 36 fills the space between the wall surface of thethrough-hole conductor 54-1 and the wall surface of the through-hole40-1, and the space between the wall surface of the through-holeconductor 54-2 and the wall surface of the through-hole 40-2. Also, thedistance between the wall surface of the through-hole 40-1 and that ofthe through-hole 40-2 is at least the thickness t of one of the metallayer.

FIG. 6 is a plan view showing the arrangement of through-hole conductors54-5 and 54-6 shown in FIG. 4. As shown in FIG. 6, these through-holeconductors 54-5 and 54-6 are disposed inside of the through-hole 40-4piercing the metal layers 30 such that the center distance between thethrough-hole conductors 54-5 and 54-6 is less than 3t. The distancebetween each center of the through-hole conductors 54-5 and 54-6 and thewall surface of the through-hole 40-4 is at least the thickness t of oneof the metal layer. The insulating member 36 fills the space formed bythe wall surfaces of the through-hole conductors 54-5 and 54-6 and thewall surface of the through-hole 40-4.

FIG. 7 is a plan view showing a modification of the arrangement of thethrough-hole conductors 54-5 and 54-6 shown in FIG. 6. As shown in FIG.7, these through-hole conductors 54-5 and 54-6 may be disposed closerthan the arrangement shown in FIG. 6. In this example, each of thethrough-hole conductors 54-5 and 54-6 and the through-hole 40-4 areconcentrically disposed such that the distance x between the center ofeach through-hole conductor and the wall surface of the metal layer 30is a certain value. This structure can stabilize the electricalcharacteristics and the magnetic properties of signals input in eachthrough-hole conductor.

A method for producing a multilayer substrate according to the presentinvention will now be described with reference to FIGS. 8A to 11B. Theproduction of the multilayer substrate according to the first embodimentwill now be described and repeated descriptions and reference numeralsin the figures will be appropriately omitted.

First, as shown in FIG. 8A, two metal layers 30-1 and 30-2 are bonded bypressing, with a bonding resin layer 32 therebetween. Thus, a metal corelayer including two metal layers is prepared. This step may be performedby laminating.

Subsequently, as shown in FIG. 8B, the metal layers 30-1 and 30-2 arepartly etched at the same time while the bonding resin layer 32 remainsat the center. Thus, the metal layers disposed at positionscorresponding to through-holes 40-1 to 40-5 and a spot-faced portion 42are removed.

As shown in FIG. 8C, a part of the bonding resin layer 32 disposed atpositions that do not include the metal layers 30-1 and 30-2 thereon isthen removed by a laser machining. Thus, the through-holes 40-1 to 40-5and the spot-faced portion 42 are formed.

Subsequently, as shown in FIG. 9B, an underlayer composed of aninsulating member 36 is formed on the bottom face of the metal corelayer. The insulating member used as the underlayer is preferablycomposed of a resin having a low fluidity.

As shown in FIG. 9E, an insulative adhesive 24-1 is then applied on thebottoms of the through-holes 40-2 and 40-3. An adhesive 24-2 having aheat dissipation effect and electrical conductivity is applied on thebottom of the spot-faced portion 42. Passive components 20-1 and 20-2and an active component 22 are disposed on the through-holes 40-2 and40-3 and the spot-faced portion 42, respectively, with these adhesivestherebetween.

Subsequently, as shown in FIG. 10A, the periphery and the inside of themetal core layer is sealed with the insulating member 36 by pressingresin layers from both sides of the metal core layer. In this step, theinsulating member 36 fills the insides of the through-holes and thespot-faced portion 42 formed in the metal core layer. In this step,resin layers having a copper foil thereon may be used as the resinlayers to be pressed. In such a case, the resin layers are pressed fromthe side having the copper foil, thereby sealing the metal core layerwith the insulating member.

Subsequently, as shown in FIG. 10B, the insulating member 36 is partlyremoved by a laser machining to form contacts 53 for connecting vias.When resin layers having a copper foil are used for sealing the metalcore layer, the copper foil is removed by etching and the lasermachining is then performed. In this step, the insulating layer filledin the through-hole 40-4 is opened so as to form a through-hole used asa through-hole conductor.

Subsequently, as shown in FIG. 11A, connecting vias 52 are formed in thecontacts for connecting vias by a semi-additive process using a copperplating. In addition, wiring layers 34-1 and 34-2 are formed on the topface and the bottom face, respectively. As a result, conductive patterns50 formed on the wiring layers 34-1 and 34-2 are connected to thepassive components 20-1 and 20-2 and the active component 22, with theconnecting vias 52 therebetween. A through-hole conductor 54 is alsoformed in the through-hole 40-4, with the insulating layer therebetween.

Finally, as shown in FIG. 11B, other wiring layers 34-3 and 34-4 areformed on the wiring layers 34-1 and 34-2 formed in FIG. 11A,respectively. Passive components 20-3 and 20-4 and an active component22-2 are mounted on the wiring layer 34-3 disposed on the top face.External terminals 56 are formed on the wiring layer 34-4 disposed onthe bottom face. The multilayer substrate is then cut along the verticallines in the figure to prepare a circuit module that can be mounted on amother board.

FIGS. 12A and 12B are cross-sectional views showing examples using ametal core layer as a GND. As shown in FIG. 12A, when the metal corelayer is used as the GND, the metal layer 30-1 and the metal layer 30-2are connected to each other, with the connecting vias 52, the conductivepatterns 50, and the through-hole conductor 54 therebetween. Thisconnected area is provided as a GND layer.

Alternatively, as shown in FIG. 12B, a conductor layer serving as athrough-hole conductor 54 may be formed on the side wall of the metalcore layer exposed by etching. The metal layer 30-1 and the metal layer30-2 may be connected to each other with this through-hole conductor 54.In the examples shown in FIGS. 12A and 12B, the metal layer 30-1 and themetal layer 30-2 are connected to each other with the through-holeconductor. Alternatively, the metal layer 30-1 and the metal layer 30-2may be connected to each other by providing the bonding resin layer 32with electrical conductivity.

According to the present invention, the height of accommodating portionof the components can be adjusted with a simple method. Therefore, thepresent invention can be applied to a substrate for a highly integratedcircuit in which various components are required to be installed.

1. A multilayer substrate comprising a plurality of components in themultilayer substrate, wherein the components are disposed inaccommodating portions provided in a metal core, and wherein the metalcore comprises a plurality of metal layers separated by one or moreintervening resin layers.
 2. The substrate of claim 1, wherein the oneor more intervening resin layers bond the metal layers.